1. Field of the Invention
A printed wiring board is prepared, by coating a photopolymerizable composition in a solution or laminating the photosensitive layer as a film resist to the copper surface of a copper-laminated board, applying imagewise exposure by actinic light, developing an image with a solvent or an aqueous alkaline solution to form a resist image on a copper substrate and then selectively applying etching or metal plating to the area of the copper surface not protected by the resist image. In this case, if the adhesion of resist film to the copper substrate is insufficient, the etching solution or the plating solution penetrates between the copper substrate and the resist film, whereby the resist is separated or lifted from the copper substrate to result in the resist chipping through etching, in the plating intrusion, and so on. This renders the picture lines or the images indistinct failing to obtain a desired circuit. This invention concerns a novel photopolymerizable composition and, more specifically, it relates to a photopolymerizable composition capable of forming a resist image with excellent adhesion to the copper surface of a copper laminated board used for the production of printed wiring boards and capable of development with a weak alkaline aqueous solution.
2. Description of the Prior Art
For the improvement in the adhesion of the resist to the copper surface, a method of adding the following compound to a photopolymerizable composition has been reported, for example, previously.
(1) Benzotriazole, benzoimidazole, benzothiazole, etc. (refer to Japanese Patent Publication No. 24035/1983)
(2) Imidazole, thiazole, tetrazole, triazole, etc. (refer to Japanese Patent Laid-Open No. 48752/1984)
(3) Diphenylthiocarbazone (refer to Japanese patent Laid-Open No. 67845/1981)
(4) Carbothioacid amide derivative (refer to Japanese Patent Laid-Open No. 113432/1984)
(5) Monoazaindole and its derivative (refer to Japanese Patent Laid-Open No. 46642/1984)
(6) Rhodanines (refer to Japanese Patent Laid-Open No. 125725/1984)
(7) Tetrazole and its derivative (refer to Japanese Patent Laid-Open No. 125726/1984)
(8) Lophine (refer to Japanese Patent Laid-Open No. 125727/1984)
(9) Theophylline (refer to Japanese Patent Laid-Open No. 125728/1984)
(10) 2-substituted-4,6-dithiol-s-triazine derivative (refer to Japanese Patent Laid-Open No. 152439/1984).
However, addition of these compounds involves problems, that the adhesion is not sufficient, or the resist film reacts with copper due to the ageing change after the coating or lamination to form a monomolecular film at the interface. This exerts an undesired effect on the succeeding step, for instance, defective etching in the etching process or insufficient peeling strength between the plated copper and resist in the plating process.